The invention relates to a steam iron pump assembly including a two-position selector with a first position for obtaining a sudden discharge of steam and a second position for obtaining a spray of cold water.
In general, steam irons comprise a heating soleplate having a series of steam outlet holes in its bottom face and a steam-generating chamber in its top face which is in communication with said holes and which also communicates with a tank of water via an adjustable low flow rate tap under the control of a rotary knob placed on the top portion of the iron.
More precisely, steam irons are generally fitted with a pump suitable for taking a quantity of water from the tank and for delivering said quantity via a selector member either into the steam-generating chamber in order to obtain a sudden and abundant discharge of steam through the holes in the soleplate, or else into a cold water spray head situated towards the front of the iron. A sudden discharge of steam or "steam surge" is advantageous for creasing thick cloth, e.g. trouser creases. Cold water is sprayed to eliminate unwanted wrinkles, in particular in cloth which is too dry.
Reference may be made, for example, to U.S. Pat. Nos. 3,747,241, 3,664,045 and 3,041,756, or else to French patent numbers 2,488,296, 2,371,540 and 2,212,457.
In a first approach, systems are proposed in which the functions associated with the pump and with the selector are separate: there is thus an independent selector connected downstream from the pump and having two outlets for directing water to one or other of two pipes associated respectively with discharging additional steam and with spraying cold water.
In general, these systems are expensive and they often suffer from leakage problems.
By way of example, particular mention may be made of U.S. Pat. No. 3,599,357 in which FIG. 8 illustrates a rotary selector mounted inside an iron and actuated by a rod extending through the top portion of the iron. The rotary selector is made in the form of a two-outlet cylindrical valve. Sealing is very difficult to obtain with such a design and its structure greatly complicates assembly operations. A more recent design of the same type, as shown in French patent number 2,439,841, may also be mentioned.
The steam iron described in that patent is still commercially available and it includes an independent selector made in the form of a tray having an inlet orifice and two outlet orifices in communication therewith, with the top of the tray being closed by a rotary actuator lever in the form of a plate having a circular bottom opening capable of putting the inlet orifice into communication with one or other of the outlet orifices, depending on the angular position of the lever.
This solution appears to be simple, but in fact it suffers from numerous problems, essentially related to keeping the rotary lever in position by means of a metal clamp having one arm pressing the lever against the tray. The rotary lever must be accurately positioned axially in order to avoid any defect in perpendicularity: and this means that the metal clamp must apply a considerable clamping force on a part which needs to be operated manually. In addition, the rotary lever itself serves to provide the sealing of the system and this is a drawback with respect to reliability in sealing. Finally, the central body of the selector is expensive to fabricate.
In another approach, attempts have been made to provide integrated assemblies in which the two functions associated with the pump and with the selector are provided by a single functional unit.
A fairly old design implementing this approach is shown in French patent number 2,137,466.
The pump assembly described in this patent comprises a pump body constituting the rotary selector of a plug-type cock or tap. The bottom portion of the pump body is then provided with a conical extension having a lateral orifice, said conical extension being surrounded by a conical rubber sleeve having two opposite orifices and prevented from rotating by a pin. Once the selector has been rotated into the desired position, a piston rod is actuated to expel water into the corresponding pipe.
Sealing is difficult with such a design in spite of a spring cup urging the pump body against the inside wall of the conical sleeve, and sealing becomes worse with aging by virtue of the rubber losing flexibility. In addition, the sleeve is subject to wear due to friction against the inevitable machining flash around the side orifice in the pump body. Finally, manufacturing tolerances are necessarily tight in order to avoid having large forces which would increase wear and, in the limit, would run the risk of jamming the rotary selector.
More recently, systems have been proposed having a rotary pump body mounted over a fixed part carrying the suction inlet and both liquid outlets, optionally together with an intermediate rotary seal.
Such a design is illustrated, for example, in French patent numbers; 2,516,561 and 2,488,659.
French patent number 2,516,561 describes a pump assembly of complex structure having a large number of gaskets, including a rotary seal in the form of a curved half-lip which is difficult to make and to install. In addition to the difficulty in obtaining sealing, this pump assembly suffers from other major drawbacks inherent to its very design: it is difficult to assemble (there are numerous close tolerances), high friction on large diameters requires lubricating grease to be employed, and the overall size of the assembly remains relatively large.
A similar design is shown in French Patent No. 2,488,659. In this pump assembly, the bottom is likewise covered by a rotary seal, however in this case the seal is also required to provide peripheral sealing, thereby further complicating the system.